4 Galileo navigation satellites sent aloft by Ariane 5

After a nearly four-month-long mission gap, Arianespace launched an Ariane 5 ES rocket from its South American spaceport in French Guiana to send four Galileo navigation satellites into orbit for Europe’s global navigation satellite system.

The flight was the first in a global launch double feature as less than 15 minutes later SpaceX’s Falcon 9 launched from the West Coast of the United States to send 10 Iridium NEXT satellites into orbit for Iridium Communications.

One of the four Galileo satellites is mated to the payload adaptor before being encapsulated inside the Ariane 5’s payload fairing. Photo Credit: Arianespace

For Arianespace, this was mission VA244. The four Galileo satellites—No. 23, 24, 25 and 26—are being launched on behalf of the European Commission. Liftoff took place at 7:25 a.m. EDT (11:25 GMT) July 25, 2018, from Kourou, French Guiana. To date, 26 satellites have been launched since 2011—12 in the last three years with the Ariane 5 rocket—with the constellation expected to be fully operational by 2020.

“With this fourth launch of the year, and the third with Ariane 5, Arianespace has proudly accomplished its 10th mission for the Galileo program,” said Arianespace CEO Stephane Israel in a statement. “I would like to thank the European Commission, and in particular DG GROW, as well as the European Space Agency, for their continued trust. More than ever, Arianespace confirms its assigned mission of guaranteeing independent and reliable access to space for Europe.”

The Galileo satellites are manufactured by OHB Systems based in Germany with launch undertaken by Arianespace, both under contract with the European Space Agency. The launch and early orbit phase was carried out by the Galileo operators SpaceOpal with CNES (the French space agency) under responsibility of the GSA, the European Global Navigation Satellite Systems.

Liftoff of Ariane 5

When the countdown reached zero, the 155-foot (47-meter) Ariane 5 ignited its liquid hydrogen/liquid oxygen-consuming Vulcain 2 engine. After about seven seconds, the engine reached full thrust and the twin side-mounted solid rocket boosters ignited, propelling the vehicle off the pad with a combined 3.4 million pounds (15,120 kilonewtons) of thrust.

After about two minutes, 20 seconds the twin booster separated and fell away, having consumed its propellant. Some seven minutes later, the core stage consumed its fuel and separated as well, leaving the upper stage in control of the mission. During its ascent, the payload faring fell away after the rocket reached 62 miles (100 kilometers) in altitude.

The second stage with its Aestus engine burned monomethyl hydrazine and dinitrogen tetroxide propellant to produce about 6,100 pounds (27 kilonewtons) of thrust for about 10 minutes before cutting off. It carried the Galileo satellites in ballistic trajectory for about three hours, eight minutes before firing for a second time—this time for about six minutes to place the satellites into a circular orbit at 14,400 miles (23,200 kilometers).

Once stabilized after the conclusion of the second burn, the Galileo dispenser released the first two satellites followed by the second pair 20 minutes later.

Galileo is the only European-based satellite navigation system that provides positioning, navigation, and timing services. The dispenser built for Galileo missions has a role of holding four satellites to secure doing liftoff and safely launch them into a nearly four-hour long flight to medium-Earth orbit (MEO).

This was the last set of Galileo satellites planned to be launched by an Ariane 5. The next set is expected to occur on top of an Ariane 6 rocket sometime in 2020 at the earliest, as that booster is still in development.

While the Galileo constellation is operational as of December 2016, it won’t be fully operational until at least 2020 when the full constellation will consist of 24 operational satellites and six active spares. Over 100 million electronic devices are using the system today, however.

Flight VA244 had a number of “lasts” for an Ariane 5 mission. According to ESA, it’s the final flight of the Ariane 5 ES variant, the last with a medium fairing, the last flight to use a EPS third stage and the last launch without the use of cryo arms from the ELA-3 launch site.

The maiden flight of the Ariane 5 ES took place in March 2008 with the Jules Verne Automated Transfer Vehicle mission to resupply the International Space Station. That cargo vehicle has also since been retired.

This was the 99th Ariane 5 launch and the third in 2018. Overall, Arianespace has launched four missions this year, including a Soyuz 2.1b rocket in March. The organization plans to fly its next mission on Aug. 21 with the flight of Vega rocket. The next Ariane 5 mission is slated for Sept. 5.

Heather Smith's fascination for space exploration – started at the tender age of twelve while she was on a sixth-grade field trip in Kenner, Louisiana, walking through a mock-up of the International Space Station and seeing the “space potty” (her terminology has progressed considerably since that time) – she realized at this point that her future lay in the stars.
Smith has come to realize that very few people have noticed how much spaceflight technology has improved their lives. She has since dedicated herself to correcting this problem. Inspired by such classic literature as Anne Frank’s Diary, she has honed her writing skills and has signed on as The Spaceflight Group’s coordinator for the organization’s social media efforts.